Cocaine is a central nervous system stimulant derived from the South American shrub Erythoxylon coca. It is commonly taken as a hydrochloride salt by nasal insuffation, intravenous injection, or smoking. Cocaine is metabolized in vivo resulting in the formation of ecgonine methyl ester, norcocaine, and benzyloecgonine. When cocaine is used, it interferes with the reabsorption of dopamine, a brain chemical associated with pleasure and movement, producing a euphoric effect. After cocaine is ingested, the user may experience constricted blood vessels, increased body temperature, faster heart rate, and higher blood pressure. Repeated cocaine use has a number of health consequences, including irregular heart beat, stroke, heart attack, and respiratory failure.
This article will discuss regulatory guidelines that have been developed for the analysis of cocaine and will present a new GC-MS method for the confirmation and quantitation of cocaine and its major metabolites, including ecgonine methyl ester, benzoylecgonine and cocathylene, in a human urine matrix. This method adheres to guidelines published by the United States Substance Abuse and Mental Health Services Administration (SAMHSA) and covers a wide range of analyte concentrations, thus reducing the need for dilutions or repeat extractions.
SAMHSA guidelines1 establish scientific and technical guidelines for federal drug testing programs, as well as standards for certification of laboratories engaged in urine drug testing for federal agencies. They describe the requirements for a confirmatory drug test, specifying that the analytical method used must combine chromatographic separation and mass spectrometric identification while also being validated before the laboratory can use it to test specimens. The guidelines indicate GC-MS as the most common confirmatory testing technology used in forensic drug testing laboratories. The method has been the gold standard since the guidelines were first introduced in 1988.
The European Workplace Drug Testing Society (EWDTS) has also published laboratory guidelines2 for legally defensible workplace drug testing, establishing best practice procedures while allowing individual countries to operate within the requirements of national customs and legislation. The guidelines relate only to the collection of urine samples, their laboratory analysis, and subsequent interpretation of the results, and must be used in their entirety. They are designed to ensure that the entire drug testing process is conducted to give accurate and reliable information about a donor's drug use. According to the guidelines, the presence of the drugs indicated by a positive screen result must be confirmed using a chromatographic technique in combination with mass spectrometry such as GC-MS. All confirmations must be quantitative.
In light of recent changes to regulatory guidelines, there is a requirement for new and more sensitive analytical methods for the confirmation and quantitation of cocaine in human urine. On May 1, 2010, SAMHSA’s revisions to the mandatory guidelines for federal workplace drug testing became effective. As part of the new guidelines, changes were made to the requirements for the confirmation of cocaine in urine, with the initial test cutoff lowered to 150 ng/mL. The method described below has been developed to satisfy these requirements, using single quadrupole GC-MS technology for precise confirmation and quantitation.